Stator cooling system for a.c. generator



Feb. 25, 1969 D. K. MAINS 3,430,035

STATOR COOLING SYSTEM FOR A.C. GENERATOR Filed March 10, 1966 Sheet WWLW Feb. 25, 1969 f D. K. MAINS STATOR COOLING SYSTEM FOR A.C. GENERATOR Filed March 10, 1966 G22 E zz :0

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United States Patent 3 Claims ABSTRACT OF THE DISCLOSURE An oil cooling system for the stator of an A.C. generator has a ring, shrunk onto the prewound A.C. stack with circumferential grooves machined in the outer surface of the ring. The assembly is fitted into a casting with O-ring seals for the grooves provided between the ring and the casting. Oil-in and oil-out passages are provided in the casting.

This invention relates to a stator cooling system for an A.C. generator.

One object of the invention is to provide a stator cooling system for an A.C. generator which is easier to construct than prior art devices.

Another object of the invention is to provide a stator cooling system for an A.C. generator wherein it is necessary to scrap fewer parts than with prior art devices.

These and other objects will be more apparent from the following detailed description taken with the drawing wherein:

FIG. 1 is a front elevational view partially in section of an A.C. generator showing one prior art cooling system;

FIG. 2 shows the stator structure for a device such as shown in FIG. 1 with the cooling system of this invention; and

FIG. 3 shows the cooling ring with the interconnecting channel between the two circumferential channels.

As shown in FIG. 1, previous oil-cooled generator frames consisted of a casting 10 containing a cast-in A.C. stack 11 and an oval cast-in tube 13 preshaped to the desired cooling circuit and welded to the A.C. stack. The tube ends are welded to a steel header (not shown) with appropriate O-ring seals provided. The previous "design required shaping of tubing to desired cross-section, forming to desired circuit, welding on headers, welding A.C. stack, sand-blasting to provide cleanliness, securing in casting fixture and casting of frame. The chief difiiculties encountered were holding the cast-in tubing in place, holding location of tube end headers and in procuring a casting free of gas pockets created by the presence of steel parts that attract and hold gas produced by the casting process. Machining of previous castings was at a reduced rate because of an intermittent steel-magnesium cut. Numerous gas pockets were exposed during machining, thereby requiring scrappage or weld-repair of the part. The A.C. stack was often scrapped along with the casting since it was cast in. An air pocket existed between the cooling tube and A.C. stack, thereby increasing the temperature rise of the windings.

This invention solves the above problems by eliminating all cast-in steel parts, including the A.C. stack, thereby providing a sound gas pocket-free casting. All passages that previously required close location in the casting have been eliminated. Machining time and difliculties are reduced by elimination of an intermittent steel out. This invention will be less expensive due to elimination of the cast-in tubing which costs more than the casting itself. Scrap rate will be reduced.

According to this invention, a hub or ring is shrunk 3,430,085 Patented Feb. 25, 1969 ICC onto the pre-wound A.C. stack and the cooling circuit and O-ring seal grooves are machined into the hub. This assembly, then, is fitted into a casting, similar to an air-cooled generator housing except containing oil-in, oil out short, axial, cored passages. This device allows the A.C. stack to be wound separately and pressed into the frame as a component. Frame weight will be reduced by approximately 15% from the old style frame.

Reference is now made to FIG. 2 of the drawing which shows a conventional cast generator housing 20 with a stator stack assembly 21 therein. The stator stack assembly has a stator stack 22 with a cooling circuit ring member 23 shrunk thereon. A pair of circumferential grooves 25 and 26 are provided in the ring member 23. A pair of O-ring grooves 27 and 28 are also provided in the ring member 23. A pair of conventional O-ring seals 31 and 32 are located in grooves 27 and 28, respectively. An interconnecting groove 33, shown in FIG. 3, is provided between grooves 25 and 26. Cooling oil is supplied to groove 25 by means of passage 34 and is taken out of groove 26 through passage 35. After the ring member 23 is shrunk onto the pre-wound A.C. stack 22, the grooves 25, 26, 27 and 28 and the interconnecting groove 33 are machined into the ring member 23. The O-ring seals 31 and 32 are then inserted into grooves 27 and 28, respectively, and the stator stack assembly 21 is pressed or shrunk into housing 20. Screws such as 37 and 38 may be used to retain the stator assembly in the housing. Cooling oil is supplied to the ring member 23 through input passage 34, flows through groove 25 through the passage 33 to groove 26 and then out through passage 35.

While two cooling grooves are shown, it is to be understood that more grooves could be provided where needed.

There is thus provided an improved stator cooling system for an A.C. generator.

While a certain specific embodiment has been described, it is to be understood that numerous changes can be made without departing from the general principle and scope of the invention.

I claim:

1. A liquid cooling system for the stator stack of an A.C. generator comprising a housing having a predetermined internal diameter; a stator assembly within said housing; said stator assembly having a stator stack with stator windings secured therein; an annular ring member secured to the outer surface of said stator stack; said annular ring member having an external diameter approximately equal to the internal diameter of said housing; a cooling circuit having a plurality of circumferential grooves in the external surface of said ring member; means for providing an interconnecting passage between said circumferential grooves; means between said cooling circuit and each edge of said ring member, for providing a seal between said ring member and said housing; and input and output channels in said housing member for supplying cooling liquid to said additional grooves.

2. The device as recited in claim 1 wherein said sealing means comprises a groove on each side of said cooling circuit with an O-ring seal in each of said grooves.

3. The device as recited in claim 2 wherein said cooling circuit comprises two circumferential grooves and an interconnecting passage between said circumferential grooves.

References Cited UNITED STATES PATENTS 1,5s1,295 8/1925 Fletcher 310-57 3,369,136 2/1968 Sanger 310-87 

